Electric plug connection and terminal box



Oct. 16, 1934. P. CHRIST ELECTRIC PLUG CONNECTION AND TERMINAL BOX FiledAug. 1'7, 1952 \\\\\\\\\\\\\\\\\&

IIII W H w gum WTORNE Y Patented Oct. 16, 1934 ELECTRIC PLUG CONNECTIONAND TERMINAL BOX Paul Christ, New York, N. Y. Application August 17,1932, Serial No. 629,140 4 Claims. (01. 247-18) This invention relatesto electrical circuit terminal boxes and connecting plugs therefor, andmore particularly to such devices related to locations where dampness ormoisture exists and 5 where gases or explosive vapors regularly orintermittently permeate the atmosphere, as for example on ships, inrefineries, gasoline filling stations or garages, paint works, or otherplaces where an electric sparkmay cause an explosion.

' The construction of such a device must be watertight in order topreven t the entrance of water or moisture to cause resulting corrosionor short-circuiting and gastight to prevent the entrance of explosivegases. Another important requisite condition is an assurancethatthecables and connections be entirely. free from stresses or strainsso that there will be no breaking or ruptures in the circuit at anypoint, and further it is l important in the 'construction of such adevice that when contact is established the" access of gas or explosivevapors to contact points in the socket be inhibited. In addition to theobjects of providing a construction that will meet the foregoingconditions, another object of the invention is to provide a simpleconstruction adapted to reduce manufacturing costs, to facilitatethesafe and facile making of connections, and to provide "an electricsocket which is universal to standard plugs so that it may be readilyused when the 3 conditions of moisture or explosive atmosphere areabsent, for the attachment of electrical devices carrying a standardplug.

'Reference is now made to the drawing for illustration of a preferredembodiment of the 'invention'in which Fig. 1 is an elevation,

Fig. 2 is a vertical section, and

Fig. 3 is a plan view of the plug and cable with the cap removed.

40 The terminal box is adapted to lie againsta wall A. The terminal box8 is internally coated with a noncorrosive paint 25 to prevent rust andat the rear of the inside of the box is a cork absorption washer '19 onwhich is mounted the terminal base 10 to which are secured the leadincircuit wires 11 introduced from the conduit '7 which has a threadedconnection with taneously cut off the potential access of any fluid orgas into the socket so that contact is actually established without anypossibility of a spark igniting an explosive atmosphere. So also inremoving the terminals 24 they lie in the socket apertures for a safeand appreciable period of time after the breakingof the circuit. Thisconstruction positively eliminates any fire hazard at this time, and anadded safeguard will be discussed hereinafter. A cover plate 1 having an05' externally screwthreaded neck portion is secured by screws 18 overthe front of the terminal box 8 and is sealed by a fluid-proof gasket19.- The auxiliary cap 2 internally threaded and provided with a rubbersealing washer 21 is attached by the chain 3 to the plate 1 and isalways screwed over the neck of the plate when the cap 4 and the plugassembly shown in Fig. 3 are removed from the terminal box. Theexternally knurled cap 4 is snugly rotatable'about the cylindricalextension 23 of the plug housing or cap 13, and. isadapted to contact acontinuous-piece and fluidtight spring washer 22' which overlies theflatshoulder formed between the plug housing 13 and theextension 23. It willnow be readily understood that the cap 4 and the continuous spring Iwasher 22 not only seal the terminal box 8 fluid-tight but also pushhome and 'hold secure the plug terminals 24 in the socket 12 causing aneasy thrust that prevents the twisting or straining of the terminals,and upon loosening the cap 4 by unscrewing it the spring washer 22 tendsto keep the electric contact as the cap is unscrewed, thereby enhancingthe rapidity of circuit-breaking. The housing 13 and the extension 23are one integral brass shell having an integral externally threaded neck20 on which is mounted an internally threaded and externally knurledretainer ring 17 which is screwed down to overlie and befrictionally-held against the shoulder formed between'theextension 23and the neck 20. The spacing between the cap 4 and the retainer ring 17in relation to the distance a: (Fig. 2) through which the cap 4 must beunthreaded for'disconnection from the neck of cover plate 1, and infurther relation to the distance y representative of the contactingrelation between the terminal points of the plug 24 and the terminals ofthe socket 10, is such that it is notpossible to remove the cap 4without the cap initially abutting ring 17, thereafter lifting the plughousing 13 and so breaking the circuit at the terminals 24. In otherwords, the distance a: through which the cap 4 is in threaded engagementwith the neck of the cover plate 1 is at least I saw Similarly in makingcontact in thev socket it is required that the cap 4 be inscrew-threaded engagement with the cover 1 before the terminal points 24are in the fixed contacting position;

The outlet cable 6 is passed through the top of the internally threadedand externally knurled sealing cap 5 which has on the inside of itscover a degree truncated conical surface 16. The cable next passesthrough a soft rubber bushing 14'the, inner end of which is in the formof a truncated cone of steep pitch and the outer end 15 of which isinthe form of a 45 degree truncatedicone. The inside of the neck 20 has aslighte ly conical seat -1 26 ,the importance of which inovercoming-fire hazards arising from strained or. mutilated connectionsin the plug will now become evident. The outer form of the softrubberbushing 14 is such that asthe sealing cap 5 is turned home the bushingis not translated lengthwise within-the neck 20 but ratheris compressedlaterally against the conical seat 26 and the seat 16 ofthe cap 5 andagainst the cable 6 from opposite directions lengthwise to hold thecable securely in the, fixed position so that external jerks-or, pullswill be absorbed entirely at the bushing. 14, thereby absolutelyrelieving the connections, of any stresses or strains and anyconsequentliability to mutilation. V s

To'sumup; My, improved, device is simple in construction and thereforelow in manufacturing. cost; ,it is watertight and gastight; it providesfor standard'plug and socket equipment thereby further reducingmanufacturing cost and providingfurther for interchangeability; itprovides for an ignition-proof make-and-break' of the plug terminals andthe socketboth'withinthe terminal box and against atmospheric gaseousmixture out-'- side the box; and it assures freedom from strains 93 on,all the electric connections.

-Having. nowshown and described oneembodiment of my invention, andrealizing that in view of my disclosure modifications in detailsandidimensions of construction will, readily occur to those skilled inthe art but within the spirit and scope. of my'inventiomI do not chooseto be limitedexcept as in the appended claims;

Iclaimz 1 V 1 1,. A fluid-tight ielectric outlet device comprisingareceptacle, angelectrical; socket member provided with terminalsand-mounted in the receptacle, thesocket member being operative toreceive the terminals of-an electric plug, a cover platefor saidreceptacle having a tubular thread- 1 ed extension therefrom, said plugbeing movable through said extensionand including a cap hav-' ing atubular extension threaded for a portion of its length, aninternallythreaded retainer ring arranged on said plug cap extension, and aclosure .I capapertured for the passage of the plug and threaded on saidthreaded extension of the cover plate, said closure cap upon initialunthreading being operative to abut said retainer ring whereby toelectrically disconnect the plug terminals from the socket terminalsprior to full unthreading from the cover plate extension.

2. A fluid-tight electric outlet device comprising a receptacle, anelectrical socket member provided with terminals and mounted in thereceptacle, the socket member being operative to receive the terminalsof an electric plug, a cover j plate for said receptacle having atubular threaded extension therefrom, said plug being movable throughsaid extension and including a cap having'a. tubular extension and athreaded neck extendingtherefrom, with a shoulder intermediate said capextension and said neck, a retainer ring operatively arranged on saidneck and engaging said shoulder, and a closure cap apertured for thepassage of the plug and threaded on said threaded extension therefrom,said'plug being movable through said extension and including acap-having a tubular extension threaded for a portion of its length, aninternally threaded-retainer, ring arranged on saidplug cap extension,and aclosure cap ,apertured for the passage of the plug and threaded onsaid threaded extension of the cover plate,jand normally spacedfrom-theretainer ring, the depth of threaded engagement of the closurecap withthe threaded extension of the closure plate being greater thanthe. normal spacing between the closure capandthe retainer ring plus theeffective depth of electrical contact between the terminals of saidsocket and said plus. a a y; 4.- A fluid-tight: electric outletdeviceoomprising a receptacle, an electricalsocketmember provided withterminals and mounted in the recep tacle,-the socket member beingoperative to receive the terminals of arr-electric plug, a .cover platefor said receptacle having a tubular threaded'extension therefrom, saidplug being movable through said extension and including a cap having atubular extension threaded for a portion of its length, with. ashoulderintermediatethe cap proper and the extension, ,a retainer ringthreaded on said cap extension, a closure cap apertured for the passageof the plug and threaded on saidthreaded extension of the cover plate, afluid-tight spring washer on the cap extension disposedbetween saidclosure cap and said shoulder ofthe plug cap, said: closure cap uponinitial unthreading being operative toabut said retainer ring whereby toelectrically disconnect the plug terminals from the-socket ,terminalsprior to full unthreading from the cover plate extension. 7

PAUL CHRIST.

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